They admitted to spying on 2 other teams in their written submission, but I simply don't believe they spied on Oxford in November then left it to Ipswich the next year then Boro?
As I posted earlier on the thread their manager is famous for his meticulous team preparation, and spends the 3 training days before every match specifically focusing on set pieces and set up against the upcoming opposition. The whistleblower also said they often discussed which set plays the opposition might use and how to counteract them in meetings and during training. Also a number of teams have apparently discussed through the season how good Southampton were at dead ball routines and how surprisingly well they nullified opposing dead ball situations.
I reckon it was systematic through the staff and systematic over the league.